What remain constant in uniform curcular motion?

A car travels 100 km at a speed of 90 km/h and returns with a speed of 30 km/h. Calculate the average speed for the whole journey.

A ball hits a wall horizontally at 8.0 m/s^-1. It rebounds horizontally at 4.4 m s^-1. The ball is in contact with the wall for 0.040 s. What is the acceleration of the ball?

What change continuously in uniform circular motion?

State whether the following statement is true of false:

Earth moves round the sun with non- uniform velocity.